C.J. van der Laken

Imaging and serum analysis of immune complex formation of radiolabelled infliximab and anti-infliximab in responders and non-responders to therapy for rheumatoid arthritis

Background: Many patients with rheumatoid arthritis are currently successfully treated with infliximab (anti-tumour necrosis factor); however, about 30% of the patients do not respond to infliximab. One of the postulated hypotheses of not responding is the fast clearance of infliximab due to the development of infliximab–anti-infliximab complexes. Objective: To investigate the in vivo mechanism of not responding and the role of human anti-chimeric antibodies (HACAs) by using radiolabelled infliximab. Methods: Two responding and two non-responding patients with rheumatoid arthritis, infused with radiolabelled infliximab, were investigated by both imaging and serum analysis. Results: Images showed predominant presence of infliximab in blood up to 24 h, with a trend of faster blood clearance and of higher liver/spleen uptake in a non-responding patient. Clinically inflamed joints showed uptake of the drug. The HACA level in the non-responders was high (1641 and 1008 U/ml), but low or not detectable in responders. Sucrose gradients of serum showed antibody complexes in both non-responders. Various sizes of antibody complexes, including very large ones, were observed in a non-responder who developed a serious infusion reaction. Conclusion: Formation of infliximab–anti-infliximab complexes were found in non-responders due to the presence of large amounts of HACA. This finding, supported by both imaging and serum analysis data, may explain failure of infliximab treatment.

SAT0667 Implementation and role of modern musculoskeletal imaging in rheumatological practice in europe

Background Modern non-X-ray imaging methods are increasingly utilised by rheumatologists though the uptake and use of these techniques has developed very differently across Europe and there is limited data on their present impact in rheumatology for individual countries. Objectives To document the current implementation, role and training in modern musculoskeletal imaging techniques: musculoskeletal ultrasound (MSUS), magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography (PET) among rheumatologists in the member countries of the European League Against Rheumatism (EULAR). Methods A EULAR Taskforce comprised of 9 rheumatologist experts in imaging developed English-language questionnaires for each imaging modality (CT, MRI, MSUS, PET) which were sent out to: national rheumatology societies of EULAR, national societies of the European Federation of Societies for Ultrasound in Medicine and Biology, the European Society for Magnetic Resonance Ultrasound in Medicine and Biology, as well as identified experts in the given modalities involved in research and/or training. The surveys were distributed via an online survey tool (Surveymonkey). Simple descriptive and summary statistics were calculated from the responses. Results A total of 205 out of 395 experts replied to the surveys. More than 90% of MSUS experts had an MSUS unit in their department. The majority of responders reported having easy access to MRI, CT or PET (56%, 78% and 50% respectively). Suspicion of rheumatoid arthritis and peripheral spondyloarthrity were the main clinical indications for performing MSUS for diagnostic purposes. Suspicion of sacroiliitis and degenerative spine disease were the most common indications to perform MRI or CT for diagnostic purposes, while PET was mainly performed to diagnose large vessel vasculitis and investigation of fever of unknown origin. When asked about the percentage of rheumatologists performing MSUS in their country 37% of experts reported less than 20%, 33% reported values between 20%–40% and 24% reported more than 40% (6%: unknown). The overwhelming majority (99%) of experts were certified in MSUS, while only 22% and 26% of experts in MRI and CT were certified in their techniques. Seventy-seven percent of responders reported that their national rheumatology societies organise MSUS courses, while courses in MRI or CT organised by the national rheumatology societies were less commonly reported (38% and 16% respectively). Conclusions Rheumatologists in Europe utilise modern imaging techniques, however access among the techniques and training offered is varied. Disclosure of Interest None declared

SAT0558 New Generation Translocator Protein Pet Tracers To Image Arthritis by Macrophage Targeting in Rheumatoid Arthritis Patients: A Proof of Concept Study

Background Previously, PET and macrophage targeting by translocator protein (TSPO) tracer [11C]-(R)-PK11195 has shown promising value to predict development of RA in the very early arthralgia phase, and flares in clinical remission. Nevertheless, the tracer [11C]-(R)-PK11195 showed rather high peri-articular background uptake which may limit detection of more subtle arthritis activity. In preclinical setting, our group recently showed more favorable imaging characteristics of two new candidate high affinity translocator protein (TSPO) tracers, [11C]DPA-713 and [18F]DPA-714, to visualize arthritis. Objectives To investigate the imaging potential of [11C]DPA-713 and [18F]DPA-714 as compared to [11C]-(R)-PK11195 for visualization of inflamed joints of RA patients using PET-CT. Methods RA patients with at least two clinically inflamed hand joints were included. PET-CT scans of their hands were obtained after intravenous injection of [18F]DPA-714, [11C]DPA-713 or [11C]PK11195. Two different tracers were compared per patient, respectively [11C]PK11195 vs. [18F]DPA-714 or [18F]DPA-714 vs. [11C]DPA-713. Quantitative analysis was done by drawing volumes of interest (VOI) over joints with visually elevated tracer uptake and background VOIs were drawn on metacarpal bone. Standardized Uptake Values (SUVs) and target-to-background (T/B) ratios were determined. Data of the tracer [18F]DPA-714 were pooled for analysis. Furthermore, blood was drawn to investigate TSPO receptor polymorphism because a TSPO rs6971 polymorphism is believed to show lower binding affinity (1). Results Nine RA patients (female3/9; age 54±18; RF+ 7/9; aCCP+ 6/9) were included with a DAS28 of 4.7±1.4 at inclusion. Clear visualization of arthritic joints was obtained with all three tracers. The absolute uptake (SUV) in arthritic joints was comparable for all 3 tracers with a trend of slightly higher uptake of [11C]DPA-713 (Table). However, T/B ratios of both [18F]DPA-714 and [11C]DPA-713 were higher than of [11C]PK11195 respectively almost 2-fold higher of [18F]DPA-714 and 2,5-fold of [11C]DPA713 (Table). Although the “low binding” TSPO polymorphism rs6971 was present in 3/9 patients, PET outcome was not different from patients without the polymorphism. [11C]PK11195 [18F]DPA714 [11C]DPA713 SUV (mean ± SD) 1.5±0.1 1.5±0.2 1.7±0.1 T/B ratios (mean ± SD) 2.4±0.2 4.2±0.7 5.6±3.4 Conclusions This is the first study that shows excellent arthritis imaging with both new generation TSPO tracers, [11C]DPA-713 and [18F]DPA-714, in active RA patients. Although imaging outcome was slightly more favorable of [11C]DPA-713, both tracers performed well with higher target-to-background as compared to the previously investigated macrophage tracer [11C]PK11195. The tracers provide opportunities for potential clinical applications of both early diagnosis and therapy monitoring of RA disease activity. References Zanotti-Fregonara et al., ACS Chem. Neurosci. 2014, 5, 963–971,dx.doi.org/10.1021/cn500138n Disclosure of Interest None declared

OP0222 Non-Invasive Pet Imaging of B-Cells in RA Patients Initiating Rituximab Treatment

Background In last decade rituximab (RTX), a B-cell targeted monoclonal antibody, has been introduced to treat rheumatoid arthritis (RA) patients but with variable response rates (30-50%). To increase treatment efficacy and reduce costs, treatment should be individualized to match the spectrum of RA. B-cell targeted therapy has been hypothesized to be most effective in a more B-cell mediated RA disease, possibly correlated to serological status (1). Whole body Positron Emission Tomography (PET) is capable to show B-cells targeting with high specificity in lymphoma patients using 89Zr-RTX (2). In addition, our group previously demonstrated the potential of PET for non-invasive visualization of immunological targets in RA (3). Objectives To investigate the feasibility of non-invasive imaging of B-cells in RA patients who initiate RTX treatment by [89Zr]RTX PET-CT. Methods Anti-B cell therapy naïve RA patients (n=20; female18/20; age 53±11; 65% IgM RF/a-CCP +) with clinical arthritis in at least two hand joints, who were eligible for RTX treatment, were included. Directly after the first therapeutic RTX infusion (1000 mg, without methylprednisolone), 18MBq [89Zr]-10 mg RTX was administered. Whole body PET-CT and detailed images of wrists and hands (22 joints/patient) were acquired at 3, and in addition, in a subpopulation at 6 days post-injection (p.i.). Thereafter, RTX treatment was continued according to standard clinical protocol. Areas of enhanced uptake on PET were defined and quantified as maximum standardized uptake values (SUVmax). Wrist and hand joints were clinically assessed for swelling and tenderness. Results Visually, all patients showed at least one hand joint with increased focal tracer uptake (87/440 joints; mean/patient ± SD 4.4±4.9) (Figure 1) with distribution: metacarpophalangeal (n=44/200), proximal interphalangeal (n=22/200) and wrist joints (n=21/40). Interestingly, 66% of PET-positive joints (57/87) corresponded to clinical findings of arthritis, while PET additionally displayed possible subclinical disease activity in another 30 joints (34%). Quantitative analysis showed high mean SUVmax values of hotspots in hand joints (2.98±1.46) which were up to 4 times higher than maximum background uptake, but varying between patients (range SUVmax 1.2-8.0), regardless of serological status. Stability of joint uptake was found over time (3-6 days p.i.) while the tracer cleared from circulation, pointing at specific binding in joints. Whole body PET-CT also demonstrated tracer uptake in extra-articular tissues especially in liver, spleen and in 5/20 patients slightly enhanced uptake in at least one peripheral lymph node. Conclusions [89Zr]RTX PET-CT seems to be a sensitive tool for in vivo identification of B-cells in arthritic joints and extra-articular tissues in RA patients. Whether quantitative differences in uptake (articular and body distribution) correlate to clinical and RTX response data is currently investigated in a prospective study. References Isaacs JD et al; Ann Rheum Dis 2013. Muylle K et al; Ann Oncol 2008. van der Laken CJ et al; Arthritis Rheum 2008. Acknowledgements This study was financially supported by Hoffmann-La-Roche,The Netherlands Disclosure of Interest S. Bruijnen: None declared, M. Tsang-A-Sjoe: None declared, H. Raterman: None declared, T. Ramwadhdoebe: None declared, D. Vugts: None declared, G. Van Dongen: None declared, M. Huisman: None declared, O. Hoekstra: None declared, P. Tak Grant/research support from: P.P. Tak participated in this study from his position at the Academic Medical Center, Amsterdam, The Netherlands. GSK did neither sponsor this study nor supported this study otherwise. P.P.Tak also has affiliations at Cambridge and Ghent but his activities at these locations were not involved in the current study., A. Voskuyl: None declared, C. van der Laken: None declared

A7.14 Effect of prednisone on type I interferon signature in rheumatoid arthritis: consequences for response prediction to rituximab

Background Elevated type I IFN response gene (IRG) expression has been described to be clinically relevant in predicting the non-response to rituximab in rheumatoid arthritis (RA) patients. Interference between glucocorticoids and type I IFN signalling has been demonstrated in vitro. Since the use and dose of oral GCs is highly variable among patients prior to the start of treatment with rituximab, we aimed to determine what the effect of GC usage is on the IRG expression in relation to the clinical response to rituximab. Methods In two independently recruited cohorts of biologic-free RA patients (n = 32 and n = 182) and a third cohort of 40 RA patients that were candidates for rituximab therapy, peripheral blood gene expression of 8 IRGs was determined by microarray or multiplex quantitative (q)PCR, and an IFN-score was calculated. The baseline IFN-score was tested for its predictive value towards rituximab response in relation to GC use using Receiver Operating Characteristics (ROC) curve analysis in the rituximab cohort. All patients in the cohorts fulfilled the revised American College of Rheumatology (ACR) 1987 criteria for the diagnosis of RA. GC use consisted of oral prednisone in doses varying from 2.5–10 mg/day and occurred in 19%, 29% and 70% of the patients in the three cohorts, respectively. The clinical response to rituximab was determined after 6 months of therapy based on the change in 28 joints Disease Activity Score (∆DAS28); patients with ∆DAS28 > 1.2 were considered responders. Results In all three cohorts, we consistently observed suppression of IRG expression in patients using prednisone compared to patients that were not using prednisone. The suppression appeared to be dose-dependent as it was most pronounced in the highest dose-range (>10 mg/day). In the rituximab cohort, separate ROC analysis on PREDN- patients alone revealed improved prediction of non-response to rituximab based on baseline IRG expression, with an AUC of 0.969 compared to 0.848 when analysed in all patients, whereas prednisone use itself had no predictive value in this cohort. Using a group-specific IFN-score-cutoff for all patients and PREDN- patients alone, sensitivity increased from 41% to 88%, respectively, combined with 100% specificity. Conclusion Because of prednisone-related suppression of the IFN-score, higher accuracy of rituximab response prediction was achieved in PREDN- patients. These results suggest that the IFN-score-based rituximab response prediction modell could be improved upon implementation of prednisone use. Disclosure CLV is an inventor on a patent wherein the predictive value of IFN type I response activity for the prediction of the clinical outcome of B cell depletion therapy via rituximab is claimed. CLV, SV and TdJ are inventors on a patent application wherein the use of the information on the interference of GCs to modulate the IFN system to improve outcome predictions on the use of biologics such as rituximab in chronic inflammatory and other conditions is claimed